the 404 Schueler Magnun was a maybe pre WW 1 improvement of the 404 by Schueler
some years ago one case was found in the old proof house in zella mehlis behind an old board after being there for 80 -90 years iirc, by the old master Ziegenhahn. he had made a chamber reamer and at least one rifle, brass can be made from 460 weatherby cases. the cartridge is also in the 460 weatherby class and much to heavy but cool!

http://www.municion.org/

the Zi-Di headstamp is an old Ziegenhahn trademark, its a reworked weatherby case
any 404 rifle can be changed into the 404 Magnum